Stem cells bear great promise for treatment of myocardial infarctions. Before this therapy becomes a reality in the clinics, in vivo studies using animal models are necessary to address important questions such as 1) whether the microenvironment in which stem cells are grafted provides enough stimuli for them to differentiate into cardiac myocytes, 2) whether adult stem cells (e.g. bone marrow derived mesenchymal stem cells) in addition to embryonic stem cells can undergo a full cardiogenic differentiation, 3) to what extent after grafting, the cardiac functions can be stabilized or improved. To address the above questions, this project will develop a non-invasive imaging system that allows repetitive, in vivo monitoring of the fate of stem cells and assessment of their potential therapeutic effect. By utilizing cardiac specific marker genes detectable by imaging, we will test whether the microenvironment into which stem cells are grafted provides enough cues for them to differentiate into the target tissue (i.e., cardiac muscle cells). By developing cine-based tagged MR imaging techniques, changes of regional myocardial contractile function resulted from the stem cell grafting will be assessed non-invasively. Finally, developing these imaging techniques on a murine myocardial infarct model allows the utilization of transgenic or knockout mouse models in the future.